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oom: deprecate oom_adj tunable

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/proc/pid/oom_adj is now deprecated so that that it may eventually be
removed.  The target date for removal is August 2012.

A warning will be printed to the kernel log if a task attempts to use this
interface.  Future warning will be suppressed until the kernel is rebooted
to prevent spamming the kernel log.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Rientjes 2010-08-09 17:19:47 -07:00 committed by Linus Torvalds
parent a63d83f427
commit 51b1bd2ace
4 changed files with 39 additions and 0 deletions
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25
Documentation/feature-removal-schedule.txt
View File

@ -151,6 +151,31 @@ Who: Eric Biederman <ebiederm@xmission.com>
---------------------------
What: /proc/<pid>/oom_adj
When: August 2012
Why: /proc/<pid>/oom_adj allows userspace to influence the oom killer's
badness heuristic used to determine which task to kill when the kernel
is out of memory.
The badness heuristic has since been rewritten since the introduction of
this tunable such that its meaning is deprecated. The value was
implemented as a bitshift on a score generated by the badness()
function that did not have any precise units of measure. With the
rewrite, the score is given as a proportion of available memory to the
task allocating pages, so using a bitshift which grows the score
exponentially is, thus, impossible to tune with fine granularity.
A much more powerful interface, /proc/<pid>/oom_score_adj, was
introduced with the oom killer rewrite that allows users to increase or
decrease the badness() score linearly. This interface will replace
/proc/<pid>/oom_adj.
A warning will be emitted to the kernel log if an application uses this
deprecated interface. After it is printed once, future warnings will be
suppressed until the kernel is rebooted.
---------------------------
What: remove EXPORT_SYMBOL(kernel_thread)
When: August 2006
Files: arch/*/kernel/*_ksyms.c

3
Documentation/filesystems/proc.txt
View File

@ -1285,6 +1285,9 @@ scaled linearly with /proc/<pid>/oom_score_adj.
Writing to /proc/<pid>/oom_score_adj or /proc/<pid>/oom_adj will change the
other with its scaled value.
NOTICE: /proc/<pid>/oom_adj is deprecated and will be removed, please see
Documentation/feature-removal-schedule.txt.
Caveat: when a parent task is selected, the oom killer will sacrifice any first
generation children with seperate address spaces instead, if possible. This
avoids servers and important system daemons from being killed and loses the

8
fs/proc/base.c
View File

@ -1037,6 +1037,14 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf,
return -EACCES;
}
/*
* Warn that /proc/pid/oom_adj is deprecated, see
* Documentation/feature-removal-schedule.txt.
*/
printk_once(KERN_WARNING "%s (%d): /proc/%d/oom_adj is deprecated, "
"please use /proc/%d/oom_score_adj instead.\n",
current->comm, task_pid_nr(current),
task_pid_nr(task), task_pid_nr(task));
task->signal->oom_adj = oom_adjust;
/*
* Scale /proc/pid/oom_score_adj appropriately ensuring that a maximum

3
include/linux/oom.h
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@ -2,6 +2,9 @@
#define __INCLUDE_LINUX_OOM_H
/*
* /proc/<pid>/oom_adj is deprecated, see
* Documentation/feature-removal-schedule.txt.
*
* /proc/<pid>/oom_adj set to -17 protects from the oom-killer
*/
#define OOM_DISABLE (-17)